Current-regulating apparatus

ABSTRACT

Apparatus for regulating the current in a circuit comprises a thermally sensitive bimetallic conductor exerting a force on a plurality of stacked resistance elements, both the bimetallic conductor and the stacked elements forming conductive parts of the circuit. The force exerted by the bimetallic conductor varies in accordance with changes in its temperature. The effective resistance of the stacked resistance elements varies inversely to the force exerted on them. The bimetallic conductor may be one which is responsive to a threshold temperature.

7 United States Patent [72] Inventor Ralph W. Alten Detroit, Mich. [21Appl. No. 812,642 [22] Filed Apr. 2, 1969 [45] Patented Dec. 7, 1971[73] Assignee Essex International lnc.

Fort Wayne, Ind.

[54] CURRENT-REGULATING APPARATUS 17 Claims, 3 Drawing Figs.

[52] 11.8. C1 338/20, 338/31,338/10l [51] lnt.Cl l-l01c 7/10 [50] Fieldof Search 338/31, 101,115,113, 20; 323/68 [56] References Cited UNITEDSTATES PATENTS 1,873,499 8/1932 Steinmayer 338/31 X 2,403,534 7/1946Kehse 3,205,709 9/1965 Gearingetal.

Primary Examiner-Rodney D. Bennett, Jr. Assistant Examiner-Richard E.Berger Att0rneyLearman and McCulloch PAT-ENTED 0E1: Yum 1625348 4 l2 I0I20 '8 2o 24 22 '5 E E I6 I 24b E) FIGI.

FIG. 3.

INVENTOR RALPH W. ALTEN CURRENT-REGULATING APPARATUS This inventionrelates to apparatus for regulating the current in a current-conductivecircuit and more particularly to a current regulator constructionemploying a variable resistance the resistance of which is adjusted byspringlike bimetallic element forming a part of the current-conductivecircuit.

Devices for interrupting or regulating current have been employed in thepast and in general have operated to break the continuity of the circuitin the event of electrical malfunction or overload. This is particularlyundesirable if the device to which the current normally is supplied isone to which at least some current must be supplied at all times if thedevice is to function as intended.

Current regulators of the type disclosed herein may be utilized ineither AC or DC circuits, and conveniently may be employed in theautomotive field to control the current to window lift motors, seatadjustment motors, and the like. Apparatus constructed according to theinvention is particularly adapted for use in a vehicle lamp circuitinasmuch as an overload current supplied to the lamps can be limited toa safe value for a sufficient length of time to enable a vehicleoperating at night to reach a repair station.

A current regulator according to the invention comprises a compressibleand expansible stack or column of individual resistance elements, suchas carbon discs, and a bimetallic element bearing forcibly against thecolumn. The force with which the bimetallic element bears against thestacked discs determines the state of compression of the stack and theeffective electrical resistance thereof. The current to be regulatedpasses through the carbon discs and through the bimetallic element,thereby heating the latter. The bimetallic element deflects in responseto changes in its temperature so as to increase or decrease theresistance of the stacked resistance elements and decrease or increase,respectively, the current without interrupting the circuit.

The principal objectives and advantages of the invention will be pointedout specifically or will become apparent from the following descriptionwhen it is considered in conjunction with the appended claims and theaccompanying drawings, in which:

FIG. 1 is an exploded view of the parts comprising a current regulatorconstructed according to the invention, the casing being shown insection;

FIG. 2 is an exploded perspective view illustrating the relativepositions of the parts of the current regulator, the casing beingomitted; and

FIG. 3 is a longitudinal sectional view of the apparatus with the partsshown in assembled relation.

Apparatus constructed according to the invention comprises a casingformed of any suitable insulating material such as plastic or fiber andhaving a bore 12 therein internally threaded at one end as at 12a. Thecasing 10 is open at one end and at the other end has an end wall 10a onwhich may be mounted a terminal connector 14 by means of a rivet 15passing through a suitable aperture formed in the flange 14a of theconnector 14 and through an aperture 16 formed in end wall 10a. A metaldisc 18 is mounted on the inside of the wall 100 and has an aperture 18atherein adapted to receive the rivet 15. The end of the rivet 15 ispeened over to form a head 15a for maintaining assembled the flange 14a,the wall 10a and the disc 18.

The apparatus includes a plurality of conductive resistance members 20arranged in a column or stack. The members 20 preferably are carbondiscs. The extreme left-hand carbon disc has an opening 20a to receivethe rivet head 15a. The other discs need not be apertured.

Threaded into the open end of the casing 10 is an externally threadedcap member 22 formed of insulating material. Connected to the cap 22 bymeans of a rivet 15b is one end of a bimetal member or spring 24, theopposite end of which is free. The member 24 is fabricated from twoback-to-back metal strips 24a and 24b bonded together and havingdifferent coefficients of thermal expansion, whereby the member 24 willdeflect in a manner well known in the art in response to a change in itstemperature. The bimetallic member 24 normally is generally U-shapedwith the higher expansive strip 24a being on the outside of the U.

The member 24 serves as a compression spring which exerts a forceagainst one end of the column of carbon discs 20 tending to compress thestack of discs between the member 24 and the housing wall 10a. Aconductive, metal disc 21 may be provided between the column of carbondiscs and the free end of the bimetal member 24 to provide suitableelectrical contact and protect the end disc from damage by contact withthe free end of the bimetal member 24. The rivet 15b passes throughapertures formed in a terminal connector 25 and in the cap 22.

Although practically all conventional bimetallic members are suitablefor use in the construction disclosed herein, bimetallic material of thetype sold under the trademark Saflex by Wilco Manufacturing Company anddescribed in its I969 Bulletin is preferred. Such material is preferredbecause, at temperatures below a predetermined or threshold temperature,an increase in temperature of the bimetallic member will cause thelatter to deflect in one direction, and at temperatures above thepredetermined temperature, an increasing temperature will cause thebimetallic member flex in the opposite direction. For example, attemperatures below a threshold temperature of approximately 250 F., anincrease in temperature will cause the free end of the bimetallic member24 to advance toward the carbon pile and apply more force thereon,thereby reducing its effective resistance and permitting more current toflow therethrough. At temperatures above about 250 F., however, the freeend of the bimetallic member 24 will more in the opposite direction soas to reduce the force on the carbon, thereby increasing the resistanceof the column of carbon and reducing the current flow. The temperatureof the bimetallic member, of course, is proportional to the currentflowing therethrough.

In operation, the current regulator is connected by means of theterminals 14 and 25 in the circuit in which the current is to belimited. Current thus may pass through the connector 14, the rivet 15,the metal disc 18, the carbon discs 20, the metal disc 21, the bimetalmember 24, the rivet 15b, and finally the terminal 25. The member 24 maybe preloaded to varying degrees by means of the closure 12. if the flowof current through the bimetallic element 24 is insufficient to heat themember 24 above its threshold temperature, the member 24 will tend toflex in such manner as to cause its free end to move toward the stack ofcarbon discs, thereby compressing the stack and decreasing theresistance to current flow. When there is sufficient current to heat themember 24 above its threshold temperature, as will be the case when anoverload current flows, the member 24 will flex in such manner as tocause its free end to move in the opposite direction or away from thecolumn of carbon discs. This will decrease the force exerted on thestack of discs and permit the column of discs to expand, therebyincreasing the effective electrical resistance in the circuit to limitthe flow of overload current. When the overload current has diminished,the member 24 will cool and flex in such direction as to increase theforce exerted on the stack of carbon discs, whereby the cycle may berepeated.

If the member 24 is formed of Saflex or equivalent material and is atany given time at its threshold temperature, a change in its temperatureeither above or below the threshold temperature will cause it to flex insuch direction as to reduce the force applied on the carbon pile, thusincreasing the resistance of the latter. If the member 24 is formed ofconventional bimetal material, however, any increase in its temperaturewill result in a lessening of the force applied on the carbon discs.

The disclosed embodiment is representative of the presently preferredform of the invention but is intended to be illustrative rather thatdefinitive thereof.

lclaim:

l. Current-regulating apparatus for regulating the current in a circuit,said apparatus comprising expansible and compressible resistance meansforming part of said circuit, the resistance of said resistance meansbeing variable according to its state of compression, and a generallyU-shaped, bimetallic, thermally sensitive, force-applying spring meansforming part of said circuit and having opposite ends one of which actson said resistance means to apply a compressive force thereto, the forceexerted on said resistance means by said force-applying means beingvariable according to the temperature thereof.

2. Current-regulating apparatus for regulating the current in a circuit,said apparatus comprising a casing; a stack of electrically conductive,individual resistor elements in said casing; and electricallyconductive, spring means reacting between said casing and said stack andexerting a force on the latter tending to compress said stack, saidspring means being operative to flex in response to a change in itstemperature either above or below a predetermined temperature anddecrease the force exerted on said stack.

3. The apparatus set forth in claim 2 wherein said spring meanscomprises a generally U-shaped electrically conductive, bimetalliccompression spring.

4. Current-regulating apparatus for regulating the current in a circuit,said apparatus comprising expansible and compressible resistance meansforming part of said circuit, the resistance of said resistance meansbeing variable according to its state of compression; and means forvarying, without interrupting, the current in said circuit and includingthermally sensitive, force-applying spring means forming part of saidcircuit and acting on said resistance means to apply a compressive forcethereto, the force exerted on said resistance means by said forceapplying means being variable according to the temperature thereof.

5. Current regulating apparatus for regulating current in a circuit,said apparatus comprising a casing; a stack of electrically conductive,individual resistor elements in said casing; and means responsive to avariation in the current flow in the circuit for varying, withoutinterrupting, the current in said circuit and including a generallyU-shaped, electrically conductive, bimetallic spring reacting betweensaid casing and said stack and exerting a force on the latter tending tocompress said stack, said bimetallic spring being operable to flex inresponse to a change in it temperature and thereby vary the forceexerted on said stack.

6. The apparatus set forth in claim 5 wherein said bimetalliccompression spring comprises back-to-back metal strips each having adifferent coefficient of thermal expansion, one side of one of saidstrips being in bearing relation with both said casing and said stack ofelements.

7. Current regulating apparatus for regulating current in a circuit,said apparatus comprising electrically conductive, compressible andexpansible resistance means having an effective resistance which variesaccording to its state of compression; and electrically conductive,thermally responsive spring means exerting force on said resistancemeans for varying, without interrupting, the current flow in saidcircuit, said force applying means being electrically connected withsaid resistance means so that a current in said circuit may flow throughsaid resistance means and said force-applying means, said force-applyingmeans being responsive to variations in said current to change the forceexerted on said resistance means and vary the efiective resistancethereof.

8. Apparatus as set forth in claim 4 wherein said resistance means andsaid force-applying means are in series.

9. Apparatus as set forth in claim 4 wherein the temperature of saidforce-applying means is dependent on the flow of current through saidresistance means.

10. Apparatus as set forth in claim 4 wherein the force exerted by saidforce-applying means on said resistance means decreases in response toan increase in the temperature of said force-applying means.

l1. Apparatus as set forth in claim 4 wherein the force exerted by saidforce-applying means on said resistance means increases in response to adecrease in the temperature of said force-applying means. I

12. Apparatus as set forth in claim 1 including a casing having an openend and closure means removably mounted on said casing to close the openend thereof, said bimetallic member being mounted within said housingand having its other end bearing on said closure means.

13. Apparatus as set forth in claim 5 wherein flexing of said bimetalliccompression spring in a manner to decrease the force exerted on saidstack is dependent on an increase in temperature of said spring.

14. Apparatus as set forth in claim 5 wherein flexing of said bimetalliccompression spring in a manner to increase the force exerted on saidstack is dependent on a reduction in temperature of said spring. 1

15. Apparatus as set forth in claim 7 wherein said force-applying meanscomprises a bimetallic conductor.

16. Apparatus as set forth in claim 15 wherein said bimetallic conductoris substantially U-shaped.

17. Apparatus as set forth in claim 16 wherein said bimetallic conductoris composed of back-to-back metal strips having different coefficientsof thermal expansion, the higher expansion strip constituting the outerpart of the U.

1. Current-regulating apparatus for regulating the current in a circuit,said apparatus comprising expansible and compressible resistance meansforming part of said circuit, the resistance of said resistance meansbeing variable according to its state of compression; and a generallyU-shaped, bimetallic, thermally sensitive, force-applying spring meansforming part of said circuit and having opposite ends one of which actson said resistance means to apply a compressive force thereto, the forceexerted on said resistance means by said force-applying means beingvariable according to the temperature thereof.
 2. Current-regulatingapparatus for regulating the current in a circuit, said apparatuscomprising a casing; a stack of electrically conductive, individualresistor elements in said casing; and electrically conductive, springmeans reacting between said casing and said stack and exerting a forceon the latter tending to compress said stack, said spring means beingoperative to flex in response to a change in its temperature eitherabove or below a predetermined temperature and decrease the forceexerted on said stack.
 3. The apparatus set forth in claim 2 whereinsaid spring means comprises a a generally U-shaped electricallyconductive, bimetallic compression spring.
 4. Current-regulatingapparatus for regulating the current in a circuit, said apparatuscomprising expansible and compressible resistance means forming part ofsaid circuit, the resistance of said resistance means being variableaccording to its state of compression; and means for varying, withoutinterrupting, the current in said circuit and including thermallysensitive, force-applying spring means forming part of said circuit andacting on said resistance means to apply a compressive force thereto,the force exerted on said resistance means by said force applying meansbeing variable according to the temperature thereof.
 5. Currentregulating apparatus for regulating current in a circuit, said apparatuscomprising a casing; a stack of electrically conductive, individualresistor elements in said casing; and means responsive to a variation inthe current flow in the circuit for varying, without interrupting, thecurrent in said circuit and including a generally U-shaped, electricallyconductive, bimetallic spring reacting between said casing and saidstack and exerting a force on the latter tending to compress said stack,said bimetallic spring being operable to flex in response to a change inits temperature and thereby vary the force exerted on said sTack.
 6. Theapparatus set forth in claim 5 wherein said bimetallic compressionspring comprises back-to-back metal strips each having a differentcoefficient of thermal expansion, one side of one of said strips beingin bearing relation with both said casing and said stack of elements. 7.Current regulating apparatus for regulating current in a circuit, saidapparatus comprising electrically conductive, compressible andexpansible resistance means having an effective resistance which variesaccording to its state of compression; and electrically conductive,thermally responsive spring means exerting force on said resistancemeans for varying, without interrupting, the current flow in saidcircuit, said force applying means being electrically connected withsaid resistance means so that a current in said circuit may flow throughsaid resistance means and said force-applying means, said force-applyingmeans being responsive to variations in said current to change the forceexerted on said resistance means and vary the effective resistancethereof.
 8. Apparatus as set forth in claim 4 wherein said resistancemeans and said force-applying means are in series.
 9. Apparatus as setforth in claim 4 wherein the temperature of said force-applying means isdependent on the flow of current through said resistance means. 10.Apparatus as set forth in claim 4 wherein the force exerted by saidforce-applying means on said resistance means decreases in response toan increase in the temperature of said force-applying means. 11.Apparatus as set forth in claim 4 wherein the force exerted by saidforce-applying means on said resistance means increases in response to adecrease in the temperature of said force-applying means.
 12. Apparatusas set forth in claim 1 including a casing having an open end andclosure means removably mounted on said casing to close the open endthereof, said bimetallic member being mounted within said housing andhaving its other end bearing on said closure means.
 13. Apparatus as setforth in claim 5 wherein flexing of said bimetallic compression springin a manner to decrease the force exerted on said stack is dependent onan increase in temperature of said spring.
 14. Apparatus as set forth inclaim 5 wherein flexing of said bimetallic compression spring in amanner to increase the force exerted on said stack is dependent on areduction in temperature of said spring.
 15. Apparatus as set forth inclaim 7 wherein said force-applying means comprises a bimetallicconductor.
 16. Apparatus as set forth in claim 15 wherein saidbimetallic conductor is substantially U-shaped.
 17. Apparatus as setforth in claim 16 wherein said bimetallic conductor is composed ofback-to-back metal strips having different coefficients of thermalexpansion, the higher expansion strip constituting the outer part of theU.